基于来自 grpc 的HelloWorld，我使用自己的 proto 文件创建了一个项目。此 proto 文件还导入同一目录中的另一个 proto 文件：
MainProto.proto：
syntax = "proto3";
package MyProject;
option csharp_namespace = "MyProject";
option optimize_for = SPEED;
option cc_enable_arenas = true;
import "google/protobuf/empty.proto";
import "google/protobuf/timestamp.proto";
import "google/protobuf/wrappers.proto";
import "CommonUtils.proto";
....
接下来是一堆枚举、消息和服务，其中一些使用来自 CommonUtils.proto 的枚举/消息。
在 CMakeLists.txt 文件中，我根据 MainProto.proto 文件生成 .cc 和 .hh。但是，这似乎不会为 CommonUtils.proto 生成必要的文件，然后在 MainProto.pb.h 和其他生成的头文件中将其检测为错误。
我的问题是：
如何修改我的 CMakeLists 或 Makefile 以同时为 CommonUtils 构建标头和 cc 文件？
如何将生成的文件链接在一起以避免“未解析的外部符号”错误？
我尝试用 CommonUtils.proto 替换我的 CMakeList.txt 文件中的 proto 文件（#Proto 文件和#Generating source 行），然后替换它并使用原始的 MainProto.proto 运行，但我得到了一堆未解决的对于应从 CommonUtils.proto 导入的所有字段，生成的 MainProto.pb.h 中的外部符号错误。
我的 CMakeLists.txt 类似于 HelloWorld，只有 greeter_async_client 和 greeter_async_server 其余部分被删除：
# Copyright 2018 gRPC authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
# cmake build file for C++ helloworld example.
# Assumes protobuf and gRPC have been installed using cmake.
# See cmake_externalproject/CMakeLists.txt for all-in-one cmake build
# that automatically builds all the dependencies before building helloworld.
cmake_minimum_required(VERSION 3.5.1)
project(MainProto C CXX)
if(NOT MSVC)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
else()
add_definitions(-D_WIN32_WINNT=0x600)
endif()
find_package(Threads REQUIRED)
if(GRPC_AS_SUBMODULE)
# One way to build a projects that uses gRPC is to just include the
# entire gRPC project tree via "add_subdirectory".
# This approach is very simple to use, but the are some potential
# disadvantages:
# * it includes gRPC's CMakeLists.txt directly into your build script
# without and that can make gRPC's internal setting interfere with your
# own build.
# * depending on what's installed on your system, the contents of submodules
# in gRPC's third_party/* might need to be available (and there might be
# additional prerequisites required to build them). Consider using
# the gRPC_*_PROVIDER options to fine-tune the expected behavior.
#
# A more robust approach to add dependency on gRPC is using
# cmake's ExternalProject_Add (see cmake_externalproject/CMakeLists.txt).
# Include the gRPC's cmake build (normally grpc source code would live
# in a git submodule called "third_party/grpc", but this example lives in
# the same repository as gRPC sources, so we just look a few directories up)
add_subdirectory(../../.. ${CMAKE_CURRENT_BINARY_DIR}/grpc EXCLUDE_FROM_ALL)
message(STATUS "Using gRPC via add_subdirectory.")
# After using add_subdirectory, we can now use the grpc targets directly from
# this build.
set(_PROTOBUF_LIBPROTOBUF libprotobuf)
set(_REFLECTION grpc++_reflection)
if(CMAKE_CROSSCOMPILING)
find_program(_PROTOBUF_PROTOC protoc)
else()
set(_PROTOBUF_PROTOC $<TARGET_FILE:protobuf::protoc>)
endif()
set(_GRPC_GRPCPP grpc++)
if(CMAKE_CROSSCOMPILING)
find_program(_GRPC_CPP_PLUGIN_EXECUTABLE grpc_cpp_plugin)
else()
set(_GRPC_CPP_PLUGIN_EXECUTABLE $<TARGET_FILE:grpc_cpp_plugin>)
endif()
elseif(GRPC_FETCHCONTENT)
# Another way is to use CMake's FetchContent module to clone gRPC at
# configure time. This makes gRPC's source code available to your project,
# similar to a git submodule.
message(STATUS "Using gRPC via add_subdirectory (FetchContent).")
include(FetchContent)
FetchContent_Declare(
grpc
GIT_REPOSITORY https://github.com/grpc/grpc.git
# when using gRPC, you will actually set this to an existing tag, such as
# v1.25.0, v1.26.0 etc..
# For the purpose of testing, we override the tag used to the commit
# that's currently under test.
GIT_TAG vGRPC_TAG_VERSION_OF_YOUR_CHOICE)
FetchContent_MakeAvailable(grpc)
# Since FetchContent uses add_subdirectory under the hood, we can use
# the grpc targets directly from this build.
set(_PROTOBUF_LIBPROTOBUF libprotobuf)
set(_REFLECTION grpc++_reflection)
set(_PROTOBUF_PROTOC $<TARGET_FILE:protoc>)
set(_GRPC_GRPCPP grpc++)
if(CMAKE_CROSSCOMPILING)
find_program(_GRPC_CPP_PLUGIN_EXECUTABLE grpc_cpp_plugin)
else()
set(_GRPC_CPP_PLUGIN_EXECUTABLE $<TARGET_FILE:grpc_cpp_plugin>)
endif()
else()
# This branch assumes that gRPC and all its dependencies are already installed
# on this system, so they can be located by find_package().
# Find Protobuf installation
# Looks for protobuf-config.cmake file installed by Protobuf's cmake installation.
set(protobuf_MODULE_COMPATIBLE TRUE)
find_package(Protobuf CONFIG REQUIRED)
message(STATUS "Using protobuf ${Protobuf_VERSION}")
set(_PROTOBUF_LIBPROTOBUF protobuf::libprotobuf)
set(_REFLECTION gRPC::grpc++_reflection)
if(CMAKE_CROSSCOMPILING)
find_program(_PROTOBUF_PROTOC protoc)
else()
set(_PROTOBUF_PROTOC $<TARGET_FILE:protobuf::protoc>)
endif()
# Find gRPC installation
# Looks for gRPCConfig.cmake file installed by gRPC's cmake installation.
find_package(gRPC CONFIG REQUIRED)
message(STATUS "Using gRPC ${gRPC_VERSION}")
set(_GRPC_GRPCPP gRPC::grpc++)
if(CMAKE_CROSSCOMPILING)
find_program(_GRPC_CPP_PLUGIN_EXECUTABLE grpc_cpp_plugin)
else()
set(_GRPC_CPP_PLUGIN_EXECUTABLE $<TARGET_FILE:gRPC::grpc_cpp_plugin>)
endif()
endif()
# Proto file
get_filename_component(hw_proto "protos/mainproto.proto" ABSOLUTE)
get_filename_component(hw_proto_path "${hw_proto}" PATH)
# Generated sources
set(hw_proto_srcs "${CMAKE_CURRENT_BINARY_DIR}/mainproto.pb.cc")
set(hw_proto_hdrs "${CMAKE_CURRENT_BINARY_DIR}/mainproto.pb.h")
set(hw_grpc_srcs "${CMAKE_CURRENT_BINARY_DIR}/mainproto.grpc.pb.cc")
set(hw_grpc_hdrs "${CMAKE_CURRENT_BINARY_DIR}/mainproto.grpc.pb.h")
add_custom_command(
OUTPUT "${hw_proto_srcs}" "${hw_proto_hdrs}" "${hw_grpc_srcs}" "${hw_grpc_hdrs}"
COMMAND ${_PROTOBUF_PROTOC}
ARGS --grpc_out "${CMAKE_CURRENT_BINARY_DIR}"
--cpp_out "${CMAKE_CURRENT_BINARY_DIR}"
-I "${hw_proto_path}"
--plugin=protoc-gen-grpc="${_GRPC_CPP_PLUGIN_EXECUTABLE}"
"${hw_proto}"
DEPENDS "${hw_proto}")
# Include generated *.pb.h files
include_directories("${CMAKE_CURRENT_BINARY_DIR}")
# Targets greeter_[async_](client|server)
foreach(_target
greeter_async_client greeter_async_server)
add_executable(${_target} "${_target}.cc"
${hw_proto_srcs}
${hw_grpc_srcs})
target_link_libraries(${_target}
${_REFLECTION}
${_GRPC_GRPCPP}
${_PROTOBUF_LIBPROTOBUF})
endforeach()
我的 Makefile 是一样的：
#
# Copyright 2015 gRPC authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
HOST_SYSTEM = $(shell uname | cut -f 1 -d_)
SYSTEM ?= $(HOST_SYSTEM)
CXX = g++
CPPFLAGS += `pkg-config --cflags protobuf grpc`
CXXFLAGS += -std=c++11
ifeq ($(SYSTEM),Darwin)
LDFLAGS += -L/usr/local/lib `pkg-config --libs protobuf grpc++`\
-pthread\
-lgrpc++_reflection\
-ldl
else
LDFLAGS += -L/usr/local/lib `pkg-config --libs protobuf grpc++`\
-pthread\
-Wl,--no-as-needed -lgrpc++_reflection -Wl,--as-needed\
-ldl
endif
PROTOC = protoc
GRPC_CPP_PLUGIN = grpc_cpp_plugin
GRPC_CPP_PLUGIN_PATH ?= `which $(GRPC_CPP_PLUGIN)`
PROTOS_PATH = ../../protos
vpath %.proto $(PROTOS_PATH)
all: system-check greeter_async_client greeter_async_server
greeter_async_client: helloworld.pb.o helloworld.grpc.pb.o greeter_async_client.o
$(CXX) $^ $(LDFLAGS) -o $@
greeter_async_server: helloworld.pb.o helloworld.grpc.pb.o greeter_async_server.o
$(CXX) $^ $(LDFLAGS) -o $@
.PRECIOUS: %.grpc.pb.cc
%.grpc.pb.cc: %.proto
$(PROTOC) -I $(PROTOS_PATH) --grpc_out=. --plugin=protoc-gen-grpc=$(GRPC_CPP_PLUGIN_PATH) $<
.PRECIOUS: %.pb.cc
%.pb.cc: %.proto
$(PROTOC) -I $(PROTOS_PATH) --cpp_out=. $<
clean:
rm -f *.o *.pb.cc *.pb.h greeter_async_client greeter_async_server
# The following is to test your system and ensure a smoother experience.
# They are by no means necessary to actually compile a grpc-enabled software.
PROTOC_CMD = which $(PROTOC)
PROTOC_CHECK_CMD = $(PROTOC) --version | grep -q libprotoc.3
PLUGIN_CHECK_CMD = which $(GRPC_CPP_PLUGIN)
HAS_PROTOC = $(shell $(PROTOC_CMD) > /dev/null && echo true || echo false)
ifeq ($(HAS_PROTOC),true)
HAS_VALID_PROTOC = $(shell $(PROTOC_CHECK_CMD) 2> /dev/null && echo true || echo false)
endif
HAS_PLUGIN = $(shell $(PLUGIN_CHECK_CMD) > /dev/null && echo true || echo false)
SYSTEM_OK = false
ifeq ($(HAS_VALID_PROTOC),true)
ifeq ($(HAS_PLUGIN),true)
SYSTEM_OK = true
endif
endif
system-check:
ifneq ($(HAS_VALID_PROTOC),true)
@echo " DEPENDENCY ERROR"
@echo
@echo "You don't have protoc 3.0.0 installed in your path."
@echo "Please install Google protocol buffers 3.0.0 and its compiler."
@echo "You can find it here:"
@echo
@echo " https://github.com/google/protobuf/releases/tag/v3.0.0"
@echo
@echo "Here is what I get when trying to evaluate your version of protoc:"
@echo
-$(PROTOC) --version
@echo
@echo
endif
ifneq ($(HAS_PLUGIN),true)
@echo " DEPENDENCY ERROR"
@echo
@echo "You don't have the grpc c++ protobuf plugin installed in your path."
@echo "Please install grpc. You can find it here:"
@echo
@echo " https://github.com/grpc/grpc"
@echo
@echo "Here is what I get when trying to detect if you have the plugin:"
@echo
-which $(GRPC_CPP_PLUGIN)
@echo
@echo
endif
ifneq ($(SYSTEM_OK),true)
@false
endif